The present invention relates to improvements in internal combustion engines. More particularly, the invention is concerned with an improved connecting rod and crank-shaft arrangement in an internal combustion engine.
In conventional internal combustion engines, the crank-shaft is usually arranged below a cylinder in a manner such that the longitudinal axis of the cylinder and the crank-shaft axis lie in a common plane. Thus, when a vertically reciprocating piston which is connected to a crank-arm of the crank-shaft by means of a connecting rod reaches its uppermost position, a dead-center occurs, that is, a line passing through the points of connection of the rod to the piston and crank-arm intersects the crank-shaft axis. It has therefore been the practice to time the ignition so that combustion takes place when the crank-arm has moved past dead-center and is at an angular position relative to the longitudinal axis of the cylinder. As a result, there is a loss of compression in the combustion chamber defined in the cylinder such that upon combustion maximum thrust cannot be imparted to the piston. In addition, since the connecting rod is angularly inclined relative to the longitudinal axis of the cylinder when the piston is intermediate its uppermost and lowermost positions, there is a problem of friction occurring between the piston and the cylinder wall.
In U.S. Pat. Nos. 1,414,987 and 2,130,529, it has been proposed to arrange the crank-shaft offset from the longitudinal axis of the cylinder. However, such an arrangement does not overcome the drawback of having a dead-center occurring when maximum compression is achieved in the combustion chamber since, when the piston reaches its uppermost position, the line passing through the connection points of the connecting rod to the piston and crank-arm still intersects the crank-shaft axis. Moreover, owing to the eccentric position of the crank-shaft, excessive friction occurs between the piston and the cylinder wall on the side of the cylinder opposite the crank-shaft.